1. Field of the Invention
The present invention relates to a rotary type electric shaver.
2. Prior Art
A conventional rotary type electric shaver will be described first.
As shown in FIGS. 10 and I1, an electric shaver is equipped with at least one shaving unit 54 that consists of a circular outer cutter unit 50 and a circular inner cutter unit 52 which is rotated relative to the outer cutter unit 50.
The outer cutter unit 50 is provided with two annular blade formation regions 56a and 56b, and a plurality of hair-entry slits 62a and 62b of the same width are formed so as to be side by side in the circumferential direction and extend in substantially radial configuration, thus forming slit-form blades 58a and 58b in the annular blade formation regions 56a and 56b. For the outer slit-form blades 58a, the side walls of the ribs 64a which are formed by two adjacent slits 62a of the outer blade formation region 56a act as blade surfaces for cutting whiskers; and likewise, for the inner slit-form blades 58b, the side walls of the ribs 64b which are formed by two adjacent slits 62b of the inner blade formation region 56b act as blade surfaces for cutting the whiskers.
Here, the term "substantially radial configuration" described above refers to the fact that the respective slits 62a and 62b are formed in a straight line so that the slits extend from the inner circumferences of the respective blade formation regions 56a and 56b to the outer circumferences of the blade formation regions with the slits inclined at a prescribed angle with respect to the radial direction extending from the center of each of the outer cutter units 50. In addition, the "prescribed angle" refers to an angle in the range of 0 degrees to 90 degrees (e. g., about 10 degrees). The same is true below. The respective slits 62a and 62b are formed in the respective blade formation regions 56a and 56b at equal angular (angle .alpha.) intervals.
Furthermore, the inner cutter unit 50 is provided with inner blade bodies 60 which are disposed circumferentially. The tip ends of the respective inner blade bodies 60 are bifurcated as shown in FIG. 11, thus forming inner blade elements 60a and 60b which respectively contact the internal surfaces of the slit-form blades 58a and 58b. These inner blade elements 60a and 60b are arranged in concentric annular configurations so as to correspond to the annular blade formation regions 56a and 56b of the outer cutter unit 50.
With the structure described above, the slit-form blade 58a and inner blade elements 60a form an annular cutting blade assembly located around the outer circumference of the shaving unit 54, and the slit-form blade 58b and inner blade elements 60b form another cutting blade assembly located around the inner circumference of the shaving unit 54.
As shown in FIG. 11, in the prior art shaver, not only the thickness a and b of the respective slit-form blades 58a and 58b of the respective blade formation regions 56a and 56b of the outer cutter unit 50 are formed to be the same (a=b), but also the interior surfaces of the slit-form blades 58a and 58b arc positioned on the same plane X.
Because of this configuration of the outer cutter unit 50, the tip ends of the respective inner blade elements 60a and 60b of the inner cutter unit 52, which rotate while contacting the interior surfaces of the slit-form blades 58a and 58b, are also formed so as to be positioned on the same plane X.
However, the above-described conventional electric shaver has problems.
The slits 62a and 62b of the respective slit-form blades 58a and 58b of the outer cutter unit 50 extend from the inner circumferences to the outer circumferences of the respective blade formation regions 56a and 56b in a substantially radial configuration. Furthermore, the respective widths of the inner and outer blade formation regions 56a and 56b must be a certain predetermined size or greater in order to obtain a maximum possible effective shaving area created by the corresponding inner blade elements 60a and 60b. Accordingly, the slits 62a and 62b are generally greater in length than the holes formed in a foil blade of reciprocating type electric shavers. Moreover, the widths d of the slits 62a and 62b must also have a prescribed size or greater in order to effectively introduce whiskers thereinto.
Consequently, the respective slits 62a and 62b are inevitably formed large, and this results in that the skin tends to enter into these slits during shaving. Accordingly, it is necessary to form the slit-form blades 58a and 58b with a certain thickness so that the skin entering the slits 62a and 62b does not reach the inner cutter unit 52 and cause cutting injuries. Generally, shaving is done by holding the electric shaver in one hand and pressing it against the surface of the skin, moving the shaving unit 54 around on the skin; accordingly, the skin in contact with the area of the side-surface opening on the outer circumferential side of the slit-form blade 58a of the blade formation region 56a located at the outermost circumference of the outer cutter unit 50, tends to wrinkle up and easily enters the slits as indicated by arrows A. Accordingly, the thickness a of the slit-form blades 58a of the outermost blade formation region 56a must have a certain predetermined thickness in order to insure the safety of the user; and as a result, the thickness b of the slit-form blades 58b of the inner blade formation region 56b correspondingly has a certain thickness so as to conform with the thickness a.
Thus, the deep shaving of whiskers such as that performed by foil blades employed in reciprocating type electric shavers is difficult to accomplish.